Schmidthammer
01 Industrial carbon brushes Technical data Standard brush grades P. 04 – 07 Carbon brushes with switch off and signalling unit Maintenance and care of collectors and slip rings P. 08 – 10 Design types, basic shapes and cable shoe shapes P. 11 – 17
2014
Elektrokohle GmbH
Industrial carbon brushes Foreword Carbon brushes have many applications in the industrial and private sectors. A multitude of applications determine the geometry and designs of our industrial carbon brushes. In an electric motor the carbon brushes take on the task to apply the voltage on to the collector and thus transfer the electric current through the armature winding. For the energy transmission to rotating slip rings or linear conductor lines, primarily graphite materials and metal graphites are used. Metal graphites can conduct higher current loads due to their metal content. Static charges caused by the rotating shafts are safely diverted by our carbon brushes made of metal and silver graphite. Industrial carbon brushes made of metal graphite are also used in the grounding area. Due to the very good physical characteristics, outstanding chemical and thermal resistance and their excellent gliding properties, our graphite materials are also used in the mechanical sector as bearing and sealing materials. According to the area of application graphite and carbon materials are manufactured with various quality features. Based on our decades of experience, we develop solution suggestions together with our customers, and thereby consider the individual wishes and requirements.
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Industrial carbon brushes for wind turbines.
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Standard brush grades for carbon blocks Hard carbon Hard carbons are produced from amorphous types of carbon such as retort coke and soot. They have a firm structure, high hardness and a good cleaning effect. Hard carbons are used in commutators with flush and sometimes recessed mica insulation. The physical properties of these grades can be optimised by the use of special impregnations. Areas of use: Current collector carbon brushes, contacts, universal motors, power tools, domestic appliances.
Carbon graphite For difficult commutation, high peripheral speeds and minimizing radiointerference, carbon brushes have high electrical resistance. In connection with the good strength values these carbon brushes work in very diverse areas. Areas of use: Many domestic appliances, electrical power tools such as drilling machines, angle grinders and electrical chainsaws.
Natural Graphite carbons Natural graphite carbons are made from various graphites and carbons. Due to the mineral content, the good glide properties are combined with a slight grinding effect. The mica insulation of the collector must be recessed. Carbon brushes made of these materials are able to remove weak burrs on the collector and sliprings. Areas of use: Machines with high peripheral speeds, turbo generators, small and medium sized motors, universal motors or alternators.
T3i graphite carbon
Resin bonded graphite carbons They form an extension of the graphite carbons and primarily stand out due to their high resistance, high transient voltages and large ratio of leak to series resistance. This has a positive effect on the attenuation of commutating currents. Areas of use: Small and medium sized generators up to 30 kW, auxiliary brushes for quadrature excitation, three phase current commutator motors, regulating motors, frequency converters and universal motors.
Electrographite carbon grades Electrographite carbon brushes are produced from pre-annealed and solidified carbon material. At temperatures of over 2500°C the conversion from carbon to electrographite occurs in the graphitisation furnace. During the graphitisation the material is mostly freed of impurities. The high grade carbon brushes stand out due to their good physical values. They have good commutation characteristics, high short circuit security, high combustion resistance and good thermal conductivity. The mica insulation must be recessed. Areas of use: Direct current motors of any power output, three phase current commutator motors, alternating current motors, drive motors for trains and trams, idle power machines, slip ring power transmissions, welding convertors, universal motors, synthesisers.
E00PK electrographite carbon brush
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Metalgraphite carbons Carbon brushes containing metal are produced from graphite and other carbons, with the addition of metals. Due to the metal content they have significantly higher conductivity and lower specific resistance and a higher electrical capacity. Carbon brushes with a high copper content can be used on slip rings or shafts for energy transmission or current derivation. Areas of use: Earthing brushes, direct current low voltage machines, car starter motors, slip and exciter rings, synchronised asynchronous motors and conductor lines.
Hot pressed metal carbon brushes Grades with a high metal content are suitable for the transfer of very high energy densities. For this purpose we recommend our grades, which are produced in a special manufacturing process. Hot pressed metal carbon brushes stand out due to their excellent physical running characteristics and their high electrical capacity. Areas of use: High load carbon brushes for galvanics, welding machines, moving welding current transmissions, annealing systems, automotive carbon brushes, slip rings and conductor lines. N51 hot pressed metal carbon
Silver graphite carbons Silver graphite materials are produced from high purity graphite and silver powder. The chemical resistance of silver has a particularly positive effect when used under various climatic conditions.
S20 silver graphite carbon
Areas of use: Shaft earthing, small motors with low voltages, tachogenerators, transfer of measurement, regulating and control currents.
Proofing The characteristics of our grades can be improved using various additional treatments. According to the type of proofing the carbon brushes can for example have better gliding properties, higher strengths or lower spark formation.
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Standard brush grades for carbon plates Hard carbon brushes Brand
Specific resistance (Ohm* mm²/m)
Density (g/cm³)
Flexural strength (N/mm²)
Rockwell hardness HR 10/40
Continuous load (A/cm²)
Speed (m/s)
Voltage drop (V)
Friction Metal coefficient content µ %
H2 H4 H4S2 H6 H47 H67
40 45 45 40 250 250
1,45 1,52 1,53 1,53 1,46 1,48
18 24 23 38 20 18
110 110 112 115 102 110
7 8 8 8 8 8
25 40 40 30 40 40
n n n n h h
H6K* H6Sb* H6Mb*
5 9 5
2,20 2,80 3,40
50 60 70
124 128 130
12 14 15
25 25 25
n n n
1,56 1,55 1,34 1,52 1,60
25 24 18 35 28
112 110 60 120 120
8 8 8 8 8
45 45 45 40 45
h h h m h
n s.n. s.n. m n
1,45 1,40 1,55 1,80 1,48 1,40 1,45 1,38 1,45
18 15 12 18 15 5 7 12 10
95 90 85 100* 100* 30* 75* 75 70
8 10 10 10 10 10 10 8 8
20 25 25 35 45 60 75 25 25
n n n n n n n m m
n n n n n n n h n
m n m n m m h 30 h 45 h 55 * impregnated with metal
Carbon graphite brushes V12 H12 H16 H20 H22
250 800 500 100 1000
Graphite carbon brushes G3 G4 G6 G1 T1 TU T3 G47 G67
35 35 25 7 12 12 25 400 250
* HR 10/20
Graphite carbon brushes, resin bonded UG75 UG UG1 UG2 UG8 UG9 UG12 UG91 V421 V434* UC4 UC15 UG25
15 80 450 600 120 190 220 300 220 2400 350 14 -
1,80 1,75 1,70 1,65 1,75 1,52 1,75 1,52 1,62 1,55 1,75 1,85 1,55
16 15 31 37 18 10 22 12 18 25 27 20
100 100 110 115 100 60 105 80 90 110 120 110
8 8 5 5 8 8 8 8 10 5 9 12 8
30 35 35 35 40 40 40 40 40 35 40 35 35
n m s.h. s.h. h h h h h h h h Lubricating brushes
n n n n n n n n n n n n n * available as pellets
Silver graphite brushes** Brand
Specific resistance (Ohm* mm²/m)
Density (g/cm³)
Rockwell hardness HR 10/40
Continuous load (A/cm²)
Speed (m/s)
Voltage drop (V)
S5 S10 S20 S30 S35 S50 S60
0,03 0,05 1,00 2,00 4,00 5,00 6,00
7,80 6,80 5,20 4,30 4,00 3,20 2,90
118 110 105 103 100 95 85
35 30 28 25 20 20 20
20 20 25 25 30 30 40
s.n. s.n. s.n. s.n. s.n. n n
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Friction coefficient µ
Metal content (%)
h 95 h 90 m 80 n 70 n 65 n 50 s.n. 40 ** further silver grades on request
Electrographite carbon brushes Brand
Specific resistance (Ohm* mm²/m)
Density (g/cm³)
Flexural strength (N/mm²)
Rockwell hardness HR 10/40
Continuous load (A/cm²)
Speed (m/s)
Voltage drop (V)
ET2 E E00 E02 E04 E06 E08 E09 E09 G5* E010 E012 E31 E661 E861 E961 E062
9 16 20 22 28 32 45 49 48 52 90 45 35 40 48 52
1,32 1,57 1,46 1,57 1,60 1,63 1,58 1,62 1,62 1,60 1,42 1,60 1,60 1,60 1,62 1,62
5 20 20 22 23 26 28 25 24 27 20 26 17 14 18 15
20 110 105 110 112 115 118 120 118 120 115 115 110 115 115 118
10 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12
60 50 40 40 40 50 50 50 50 50 50 50 40 40 40 45
n n n n n n m h h h h h s.h. s.h. s.h. s.h.
Friction coefficient µ n n n n n n n n n n n m n n n h * formerly V436
Metal graphite brushes, cold pressed Brand
Specific resistance (Ohm* mm²/m)
Density (g/cm³)
Flexural strength (N/mm²)
Rockwellhardness HR 10/40
Continuous load (A/cm²)
Speed (m/s)
Voltage drop (V)
K K3 K4 KM1 2378 3316 3344 4350 5246 6235 7274 065 N46 V444
10 8 7 2 0,5 1,0 1,2 2,2 5,0 6,0 8,0 0,5 3,0 0,5
2,40 2,80 3,00 3,10 3,90 3,60 3,50 3,00 2,70 2,50 2,20 4,00 3,10 4,00
20 27 30 36 28 25 21 19 17 16 15 26 20 30
80 90 90 100 100 95 95 90 85 80 80 100 90 110
12 13 15 13 15 13 13 13 12 12 12 15 13 15
30 25 20 25 35 40 40 40 40 40 45 35 40 35
n n n n n n n n n n n n n n
n n n n n n n n n s.n. s.n. n n n
47 60 70 63 70 65 60 50 40 30 20 70 50 75
80 62 60 55 50 40 30 90 140 110 70 30 90 85 30 25 24
125 110 100 100 98 95 90 110 110 85 80 50 105 100 50 112 100
30 25 22 22 18 16 15 30 40 35 40 40 40 40 35 30 13
20 20 30 35 40 20 20 20 20 25 20 20 30 30 40
s.n. s.n. s.n. s.n. s.n. n s.n. s.n. s.n. s.n. s.n. s.n. s.n. n n
n n n s.h. s.h. n m n n n m m m n n
95 90 87 85 75 70 65 96 91 86 93 90 95,5 95 86 88 50
Friction co- Metal efficient content µ (%)
Metal graphite brushes, hot pressed 0555 1503 1531 BR 2454 3402 3450 085 N6 N8 N10 N51 N52 N55 N91 V682 V816i
0,06 0,08 0,09 0,10 0,12 0,15 0,15 0,3 0,3 0,6 0,1 0,1 0,1 0,1 0,1 0,2 2
5,50 5,30 5,00 4,90 4,30 4,20 4,00 5,40 6,00 5,00 6,10 5,50 6,70 6,60 5,20 5,65 3,00
Key Voltage drop: s.n. (very low) = < 1,0 V n (low) = 1,0 – 1,8 V
m (medium) = 1,8 – 2,5 V h (high) = 2,5 – 3,5 V s.h. (very high) = > 3,5 V
Friction coefficient: s.n. (very low) = < 0,15 n (low) = 0,15 – 0,20
m (medium) = 0,20 – 0,26 h (high) = > 0,26
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Carbon brushes with switch off and signalling unit 1. Switch off unit = AB The switch off unit is automatically effective, if the wear on the carbon is great enough that a replacement is necessary. This means that checking and monitoring the carbon brush are omitted. Our switch off device is largely temperature resistant. It can be used both for motors with low current load (power supply via carbon with spring), and for motors with high current load (power supply via carbon with strand); e.g. power tools, domestic appliances etc. Functioning: If the carbon brush has achieved its wear limit, the switch off nipple suddenly protrudes from inside it, and safely and quickly lifts the brush off from the collector. The current flow is interrupted and the machine comes to a standstill. Further damage to collector is avoided.
Residual carbon length
x
Switch off point
Holder
Switch off nipple
With our smallest switch off device the switch off point is at a residual carbon length of approx. 5.5 mm, for the medium one at approx. 7 mm and for the largest between 9 and 13 mm. The size of the switch off device depends on the carbon brush cross section.
Collector
This should be at least 2 cm². For larger carbon cross sections we recommend using our signalling device.
2. Signalling device Brush monitoring brings optimum operating security for electromotors and generators. In order to reduce the continual maintenance of current transmission systems, it was necessary to find a device which signals the upcoming breakdown of the carbon brush caused by wear, in advance.
Design shape
Cu 0,14 mm² b a
Holder
The signal contact occurs via the copper strand and the collector or slip ring. This design saves space. The carbon brush should not continue to be in operation for significantly longer after the signal. The copper strand can cause breakdown of the patina, and can also slightly attack the collector or slip ring.
a = Signalling height b = Signalling line Ø = 1 mm with insulated Cu strand
Collector Carbon brush with signalling unit
Maintenance and switching units for the signalling units are available from us.
D
C B
A
D
C B
A
1
1
M
Switching with auxiliary circuit
8
M
Switching without auxiliary circuit
Maintenance and care of collectors and slip rings Commutators and slip rings To avoid mechanical disturbances the slip rings and collectors must run smoothly. In this way brush sparking and serious burn off of the carbon brush and burning in of the running surface can be avoided. In the case of recessed mica insulation the utmost care should be taken during milling works. The following image shows what you should look out for. Image 1: a: bevel too strong, smooth operation of brush will be influenced negatively. b: recess too wide, serious brush imbalance. c: remaining residual insulation (mica) can not be worn away by soft carbon material.
b
a
c
a
a
0,1
Image 2: Here it is clear how it should be milled; a bevel is not necessary in most cases, if the collector is turned precisely. Cleanliness should be ensured, so that wear dust from the carbon brush and foreign impurities do not settle in the recessed insulation slots and hereby cause operational disturbances.
1-1,5
Edges slightly broken
Copper
Mica
Brush assembly Correct allocation of the carbon brushes on the commutator is necessary. The brush division should be as precise as possible so that good commutation, reduction of lamella sparking and balance of the polar and electrolytic effect are ensured. The carbon brushes sitting on a bolt must be aligned exactly, taking into consideration a possible designated gradation. +
Recommended gap of holder-collector: 2,5 to 3 mm
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As cathodic brushes (plus brush generator/minus brush motor) are almost always responsible + for an electrical weakening of the grinding body, it should be ensured that they are distributed as evenly as possible across its width. The distribution of the anodic carbon brushes is not significant, however it is good from a meIncorrect Correct chanical point of view, if the carbon brushes of two neighbouring bolts are precisely behind each other. This is particularly electrically necessary in the case of reverse motors, as the polarity often changes here. An axial staggering of the brushes (see image) is necessary, so that no untraveled strips emerge. In order to achieve an evenly coloured patina, the same number of brushes should be ensured in all runways as far as possible.
Attaching carbon brushes Carbon brushes for larger overlaps (t larger than 6mm) should continually be ground in. Pull a longer strip of emery cloth, which is laid out on a large part of the grinding wheel, back and forth underneath the carbon brushes. The grinding in takes place at normal brush pressure, which is given by the holder. Under no circumstances should the pressure be increased by additional pressing on by hand. For machines that run only in one direction of rotation, the emery cloth should only be pulled underneath the overlying carbon brush in the same direction of rotation. When withdrawing the brush must be lifted. The grinding in can be carried out Seating in with emery cloth and pumice stone quicker using an artificial pumice stone. This is placed in front of the carbon brush when the machine is running, so that the grains flying off cope with the grinding in procedure. In just a short time the correct radius is ground in and a flush fitting of the carbon running surface is guaranteed. After grinding in, the grinding wheel and the running surface of the carbon brush should be carefully cleaned. Hereby, it should be ensured that the dust is not blown into the winding. Artificial pumice stones (commutator grinders) are available from us.
Brush pressure The brush pressure significantly influences the correct working of the carbon brushes and is therefore an important factor, which is often not given enough consideration. The electrical and mechanical wear of the carbon brushes are significantly influenced by this. Assuming normal conditions, the brush pressures for various machines are shown in the table below as rough reference values. Machine type
Spec. brush pressure N/cm²
Machine type
Spec. brush pressure N/cm²
Universal motor (FHP)
2,0 – 4,0
Tram way motors
3,5 – 5,0
Stationary converters
1,8 – 3,0
Trolley bus motors
3,0 – 4,5
Slip ring motors
1,5 – 2,5
Traction motors
2,5 – 4,0
Steel slip rings
1,2 – 1,4
Mine railways and crane motors
4,5 – 6,0
In individual cases the brush pressure depends on the brush operating conditions and the brush grade. In case of uncertainty we can provide information about the relevant suitable brush pressure.
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Request and order details for carbon brushes The following details are necessary 1. Dimensions of the carbon brushes
a
t
a
t
Tangential direction Axial direction Radial direction
=t =a =r
r
Dimensions and tolerances are designed in accordance with DIN IEC 43000 sheet 1 + 2.
r
Commutator
2. Design of carbon brushes
Slip ring
2.1. Design types table page 11 (processing the head and running surface) 2.2. Basic shapes according to tables page 12 – 16 2.3. See image for details of visible cable length! The cable diameter is determined according to DIN 43002. Each cable can be provided with insulation. Standard: silicone tubing, other designs according to details, e.g. Diolen tubing etc.
Visible cable leng
th
x
If tin plated or silver plated cable is desired, then this must be stated on ordering. 2.4. Cable shoes and plug according to table page 17. Measurements for slot width and/or hole diameter or plug diameter must be stated. 2.5. Details on copper plating, tin plating or silver plating of the contact surfaces are desired. 2.6. If the stability of the carbon material and the cross section of the carbon brush allow it, the fastening of the cable will be carried out by tamping contact (standard design). The well designed tamping contact offers a low voltage drop and mechanically a high strain. If the carbon brushes are provided with a fitting (metal parts, bracket, support frame etc.), the fastening is carried out with rivets. If another cable fastening is required, e.g. soldering, then this must be stated.
3. Special design If carbon brushes are required, which are not included in the table, of course a delivery is possible. In such cases we ask that you send a sample or a drawing with the dimensions and designs of the carbon brush. Details about the brush grade, make and quality description, description of the purpose and details of the operating data currently being used are necessary for the correct selection of the carbon brush.
4. Mounting questions Our technical departments will help and support you in clarifying special questions about mounting and design of carbon brushes on electrical machines, power transmission equipment etc.
5. Ordering examples
Example
Quality
Dimensions t×a×r
Basic form image no.
Design type
Visible cable length mm
Cable shoe image no.
Remark
1 2
E09 3450
12,5 × 32 × 32 40 × 20 × 40
305 718
D B
80 90
53 4
Radius 100 mm Angel 45° insul. = i
M6
Example 1
Example 2
+
+
s
53
4
s
=
= +
+
r
M6
α°
r
718
305
B
t
t D
E09
10
12,5 × 32 × 32
305
a
a
D
80
53
M6
R=100
3450
40 × 20 × 40
718
B
90i
4
45°
M6
Design types
A Standard
B Dust groove
C Head slot
D Dust groove
E Head slot
H Fluting
J Head drill hole
G1 G2 G3 G4 Laminate
F Head hardening
G Head plates
K Contact bevel
L U-slot
M Head mould
N Top bevel
O Top radius
P Carbon brush layer
Q Pair of carbon brushes
R Drill hole
S Nut insert
T Twin
U Twin and cooling slot
V Dust groove
W Threads
X Nut insert
Y Head notch
Rubber
11
Basic shape
101
102
103
104
105
108
109
112
113
119
120
121
125
127
128
130
137
142
144
152
153
155
156
157
161
162
163
201
202
203
204
205
206
208
209
210
211
222
223
225
228
229
231
233
234
235
236
237
238
239
240
301
302
303
305
306
307
308
309
310
311
312
313
12
Basic shape
314
315
317
318
319
320
321
322
328
402
403
404
405
407
409
411
412
413
415
416
417
418
501
503
504
506
507
508
510
512
513
515
516
517
518
519
520
522
523
526
528
530
531
532
533
535
536
537
538
539
540
541
542
13
Basic shape
543
605
612
628
14
607
608
610
613
614
615
616
617
618
619
620
621
622
623
624
625
629
630
626
631
632
627
633
634
Basic shape
636
701
702
703
704
706
707
708
709
711
713
714
716
717
718
719
720
723
725
727
728
729
730
731
732
733
734
735
736
737
738
739
740
742
743
744
746
747
748
749
751
752
754
756
757
758
759
760
761
762
763
764
765
766
15
Basic shape
767
768
769
770
771
772
773
774
775
776
777
778
779
780
801
803
804
808
811
812
813
814
815
816
823
828
901
902
903
904
809
810
817
16
818
819
906
909
914
915
910
916
917
911
912
913
918
919
920
Cable shoe shape
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
26
27
29
30
33
34
25
31
32
39
40
48
49
41
50
51
28
35
36
37
42
45
46
52
53
38
47
54
17
18
Industrial carbon brushes in hydroelectric power stations.
Our range of products
00
Carbon blocks
01
Industrial carbon brushes
02
Midget carbon brushes
03
Micro carbonbrushes
04
Automotive carbon brushes
05
Carbon contacts | carbon rolls
06
High current carbon brushes
07
Carbon inserts
08
Carbon proďŹ les
09
Carbon vanes
10
Graphite lubricating brushes
11
Carbon bearings
12
Thermistors
13
Special armatures for brushes
14
Flexible copper conductors
15
Carbon welding rods
16
Carbon brushes for fork lift trucks
17
Holders for carbon brushes
18
Special carbon brushes
19
Schmidthammer Elektrokohle GmbH Walpersdorfer Str. 33-39 D-91126 Schwabach Fon: +49 (0)9122 - 18 06-0 Fax: +49 (0)9122 - 18 06-60 Mail: mega@schmidthammer.com
www.schmidthammer.com